Why don't construction prices go down?

The sales department then always specified a contribution margin based on the calculation, and accordingly the price was determined.

This actually happens, that management controls the contribution margin through the commission scheme. However, this is only one of many methods – and certainly not the most common.

I at least still expect 2-3%, since the calculations have always been very accurate so far.

Fingers crossed.
What strategic approach do you have for the final price negotiation?